Questioning the universe | Stephen Hawking

Summary

Renowned physicist Stephen Hawking explores the origins and future of the universe and humanity in this insightful talk. He discusses the Big Bang, the possibility of alien life, and the importance of space exploration for human survival. Hawking suggests that life may be abundant in the galaxy, but advanced civilizations might be rare due to self-destruction. He emphasizes the need for humanity to expand beyond Earth to ensure long-term survival, highlighting the progress made in understanding the cosmos and the quest for a complete theory of the universe.

Takeaways

• 🌌 The universe is the oldest and largest entity, with no known beginning or end.
• 🤔 Questions about the origin of the universe, alien life, and the future of humanity are central to our understanding of existence.
• 🔍 Before the 1920s, the universe was thought to be static, but the discovery of its expansion changed this view.
• 💥 The Big Bang theory suggests the universe began approximately 15 billion years ago from an infinitely dense point.
• 🕰 The concept of time and space being distinct is challenged by general relativity and quantum theory under extreme conditions.
• 🌱 The universe could have spontaneously created itself from nothing, with the laws of evolution determining its initial state.
• 🔮 Observations of the cosmic microwave background support the predictions of the universe's creation from different states.
• 🌍 Life on Earth likely arose spontaneously, suggesting the possibility of life on other planets with suitable conditions.
• 👽 Despite extensive searches, no definitive signs of alien civilizations have been found within a few hundred light years of Earth.
• 🌱 The probability of life appearing on a planet seems high, given the short time it took for life to emerge on Earth.
• ⚠️ The human race faces significant challenges, including population growth and the potential for self-destruction.
• 🚀 Long-term survival of humanity may depend on our ability to spread out into space and adapt to new environments.

Q & A

What was the prevailing belief about the universe before the 1920s?

Before the 1920s, it was believed that the universe was essentially static and unchanging over time.

What discovery led to the understanding that the universe is expanding?

The discovery that distant galaxies were moving away from us indicated that the universe is expanding.

What is the significance of the Big Bang theory in understanding the universe's origin?

The Big Bang theory suggests that the universe began approximately 15 billion years ago when all matter and energy were concentrated at a single point before expanding.

What challenges the traditional division of the universe's theory into laws of evolution and initial conditions?

The traditional division is challenged by the idea that under extreme conditions, time can behave like another dimension of space, merging the concepts of time and space and allowing the laws of evolution to also determine the initial state of the universe.

How does the concept of time behaving like space under extreme conditions affect our understanding of the universe's creation?

This concept suggests that the universe could spontaneously create itself out of nothing, with the laws of evolution determining not just its evolution but also its initial state.

What evidence supports the idea that life on Earth arose spontaneously?

The presence of fossils of algae from 3.5 billion years ago indicates that life appeared on Earth within half a billion years of its formation, suggesting a high probability of life appearing spontaneously.

What does the lack of evidence for alien life suggest about the existence of civilizations at our level of development within a few hundred light years?

The lack of evidence, such as radio waves or direct contact, suggests that there may be no alien civilizations at our level of development within a few hundred light years.

What is the current understanding of the probability of life appearing on other planets similar to Earth?

Given the short time it took for life to appear on Earth after its formation, it is believed that the probability of life appearing on other suitable planets is reasonably high.

What are the potential risks to the long-term survival of the human race mentioned in the script?

The potential risks include the exponential growth of population and resource consumption, along with our technical ability to significantly alter the environment, coupled with the genetic instincts that may lead to self-destruction.

What is the proposed solution to ensure the long-term survival of the human race as suggested in the script?

The proposed solution is to spread out into space, as it offers a chance to avoid the risks associated with remaining inward-looking on planet Earth.

What is the ultimate goal of Professor Hawking's quest for knowledge as mentioned in the script?

The ultimate goal is to develop a complete theory of the universe, which includes understanding its origin, evolution, and the potential for life beyond Earth.

What was Professor Hawking's personal view on the likelihood of being the only civilization within several hundred light years?

Professor Hawking believed it was quite likely that we are the only civilization within several hundred light years, as we have not detected any radio waves from other civilizations.

Outlines

00:00

🌌 The Origins and Expansion of the Universe

This paragraph delves into the fundamental questions of our existence and the nature of the universe. It starts by asserting the universe as the oldest and largest entity, setting the stage for inquiries about our origins, the emergence of the universe, and the possibility of extraterrestrial life. The speaker recounts the historical belief in a static universe, which was overturned by the discovery of its expansion. This led to the concept of the Big Bang as the universe's beginning. The narrative then explores the mysteries before the Big Bang and the implications of time and space being interconnected, suggesting the universe could have spontaneously created itself. The paragraph concludes with the remarkable alignment of these theories with observations of the cosmic microwave background, indicating a deep understanding of the universe's creation.

05:05

👽 The Probability of Alien Life and Humanity's Future

The second paragraph shifts focus to the likelihood of alien life and the future of humanity. It humorously dismisses UFO sightings and government conspiracies, suggesting a lack of concrete evidence for extraterrestrial visitation. The SETI project's failure to detect alien transmissions implies that civilizations at our level of development may not exist within several hundred light years. The speaker then transitions to a discussion on humanity's survival, highlighting the challenges posed by exponential population growth, resource depletion, and our inherent genetic traits that may hinder peaceful coexistence. The conclusion emphasizes the importance of space exploration for the long-term survival of our species, advocating for manned space flight as a step towards ensuring our future beyond Earth. The paragraph ends with a reflection on the speaker's personal quest for knowledge and the pursuit of a complete theory of the universe, underscoring the progress made and the importance of continuing this journey.

Keywords

💡Universe

The universe refers to the entirety of space and time, including all forms of matter, energy, and the physical laws that govern them. It is central to the video's theme as it discusses the origins, expansion, and the future of the universe. The script mentions that the universe is expanding, indicating its dynamic nature and leading to the concept of the Big Bang as the beginning of the universe.

💡Big Bang

The Big Bang is the prevailing cosmological model explaining the origin of the universe. It suggests that the universe began as a singularity and has been expanding ever since. In the script, the Big Bang is presented as the event approximately 15 billion years ago where all matter and energy were concentrated at a single point, marking the beginning of the universe.

💡Expansion

The term 'expansion' in the context of the universe refers to its ongoing increase in scale. The script discusses the discovery that the universe is not static but expanding, with galaxies moving away from each other, which is a key piece of evidence supporting the Big Bang theory.

💡Alien Life

Alien life refers to the hypothetical existence of life forms outside of Earth. The script raises questions about the existence of extraterrestrial life and discusses the possibility of life arising on other planets, given the right conditions, which ties into the broader theme of the search for life in the universe.

💡Initial Conditions

Initial conditions in cosmology are the state parameters at the beginning of a system's evolution, such as the universe at the Big Bang. The script mentions that understanding the initial conditions of the universe has been a challenge, but recent theories suggest that the laws of physics may determine these conditions, indicating a self-creating universe.

💡General Relativity

General relativity is a theory of gravitation proposed by Albert Einstein, which describes the curvature of spacetime due to mass and energy. The script refers to general relativity as one of the laws that determine the evolution of the universe, especially under extreme conditions where it intersects with quantum theory.

💡Quantum Theory

Quantum theory, or quantum mechanics, is the fundamental theory in physics that describes the behavior of matter and energy at the smallest scales. The script suggests that under extreme conditions, quantum theory allows time to behave like another dimension of space, merging with general relativity to influence the universe's initial state.

💡Cosmic Microwave Background

The cosmic microwave background (CMB) is a remnant radiation from the early universe, considered the afterglow of the Big Bang. The script mentions that observations of the CMB by the WMAP satellite support predictions about the universe's creation, providing evidence for the conditions of the early universe.

💡SETI

SETI stands for Search for Extraterrestrial Intelligence, a collective term for scientific efforts to detect intelligent extraterrestrial life. The script refers to SETI's extensive search for alien signals, which has so far been unsuccessful, suggesting the rarity or isolation of civilizations.

💡Human Race

The human race encompasses all human beings considered collectively. The script discusses the future of the human race, emphasizing the need for humanity to survive and continue, potentially by spreading out into space to ensure long-term survival beyond Earth.

💡Space Exploration

Space exploration is the investigation and travel into outer space. The script concludes with a strong advocacy for manned or personned space flight as a means for humanity to extend its future beyond Earth, highlighting the importance of space exploration for the survival of the human race.

Highlights

There is nothing bigger or older than the universe, emphasizing the vastness and age of the cosmos.

The universe was once thought to be static and unchanging, challenging our understanding of its dynamic nature.

The discovery of the universe's expansion and galaxies moving away from us indicates a beginning point.

The concept of the Big Bang as the universe's beginning, about 15 billion years ago.

Questions about what existed before the Big Bang and the creation of the universe.

The division of the universe's theory into laws of evolution and initial conditions, and recent progress in understanding both.

The idea that under extreme conditions, time can behave like another dimension of space, blurring the line between time and space.

The spontaneous creation of the universe from nothing, a radical departure from traditional cosmological views.

Calculating the probability of the universe's creation in different states, aligning with WMAP satellite observations.

The suggestion that we may have solved the mystery of creation, with a humorous note about patenting the universe.

The possibility of life arising spontaneously on Earth and the likelihood of its occurrence on other planets.

Fossil evidence of life appearing on Earth within half a billion years of its possibility, indicating a high probability of life's emergence.

The lack of alien contact and the implications for the existence of civilizations at our stage of development.

The SETI project's extensive search for extraterrestrial signals and the absence of detected alien civilizations.

The future of the human race and the importance of space exploration for long-term survival.

The exponential growth of population and resource use, along with the technical ability to alter the environment, posing risks to humanity.

The genetic code's inherent traits and the challenges they present for avoiding disaster in the future.

Stephen Hawking's personal journey and his quest for a complete theory of the universe.

Hawking's belief in the likelihood of human civilization being alone in the Milky Way, or the alternative of self-destruction.

The call to action for humanity to spread out into space for long-term survival and the support for manned space flight.

Transcripts

There is nothing bigger or older than the universe.

The questions I would like to talk about are:

one, where did we come from?

How did the universe come into being?

Are we alone in the universe?

Is there alien life out there?

What is the future of the human race?

Up until the 1920s,

everyone thought the universe was essentially static

and unchanging in time.

Then it was discovered that the universe was expanding.

Distant galaxies were moving away from us.

This meant they must have been closer together in the past.

If we extrapolate back,

we find we must have all been on top of each other

about 15 billion years ago.

This was the Big Bang, the beginning of the universe.

But was there anything before the Big Bang?

If not, what created the universe?

Why did the universe emerge from the Big Bang the way it did?

We used to think that the theory of the universe

could be divided into two parts.

First, there were the laws

like Maxwell's equations and general relativity

that determined the evolution of the universe,

given its state over all of space at one time.

And second, there was no question of the initial state of the universe.

We have made good progress on the first part,

and now have the knowledge of the laws of evolution

in all but the most extreme conditions.

But until recently, we have had little idea

about the initial conditions for the universe.

However, this division into laws of evolution and initial conditions

depends on time and space being separate and distinct.

Under extreme conditions, general relativity and quantum theory

allow time to behave like another dimension of space.

This removes the distinction between time and space,

and means the laws of evolution can also determine the initial state.

The universe can spontaneously create itself out of nothing.

Moreover, we can calculate a probability that the universe

was created in different states.

These predictions are in excellent agreement

with observations by the WMAP satellite of the cosmic microwave background,

which is an imprint of the very early universe.

We think we have solved the mystery of creation.

Maybe we should patent the universe

and charge everyone royalties for their existence.

I now turn to the second big question:

are we alone, or is there other life in the universe?

We believe that life arose spontaneously on the Earth,

so it must be possible for life to appear on other suitable planets,

of which there seem to be a large number in the galaxy.

But we don't know how life first appeared.

We have two pieces of observational evidence

on the probability of life appearing.

The first is that we have fossils of algae from 3.5 billion years ago.

The Earth was formed 4.6 billion years ago

and was probably too hot for about the first half billion years.

So life appeared on Earth

within half a billion years of it being possible,

which is short compared to the 10-billion-year lifetime

of a planet of Earth type.

This suggests that the probability of life appearing is reasonably high.

If it was very low, one would have expected it

to take most of the ten billion years available.

On the other hand, we don't seem to have been visited by aliens.

I am discounting the reports of UFOs.

Why would they appear only to cranks and weirdos?

If there is a government conspiracy to suppress the reports

and keep for itself the scientific knowledge the aliens bring,

it seems to have been a singularly ineffective policy so far.

Furthermore, despite an extensive search by the SETI project,

we haven't heard any alien television quiz shows.

This probably indicates that there are no alien civilizations

at our stage of development

within a radius of a few hundred light years.

Issuing an insurance policy

against abduction by aliens seems a pretty safe bet.

This brings me to the last of the big questions:

the future of the human race.

If we are the only intelligent beings in the galaxy,

we should make sure we survive and continue.

But we are entering an increasingly dangerous period of our history.

Our population and our use of the finite resources of planet Earth

are growing exponentially,

along with our technical ability to change the environment for good or ill.

But our genetic code

still carries the selfish and aggressive instincts

that were of survival advantage in the past.

It will be difficult enough to avoid disaster

in the next hundred years,

let alone the next thousand or million.

Our only chance of long-term survival

is not to remain inward-looking on planet Earth,

but to spread out into space.

The answers to these big questions

show that we have made remarkable progress in the last hundred years.

But if we want to continue beyond the next hundred years,

our future is in space.

That is why I am in favor of manned --

or should I say, personned -- space flight.

All of my life I have sought to understand the universe

and find answers to these questions.

I have been very lucky

that my disability has not been a serious handicap.

Indeed, it has probably given me more time than most people

to pursue the quest for knowledge.

The ultimate goal is a complete theory of the universe,

and we are making good progress.

Thank you for listening.

Chris Anderson: Professor, if you had to guess either way,

do you now believe that it is more likely than not

that we are alone in the Milky Way,

as a civilization of our level of intelligence or higher?

This answer took seven minutes, and really gave me an insight

into the incredible act of generosity this whole talk was for TED.

Stephen Hawking: I think it quite likely that we are the only civilization

within several hundred light years;

otherwise we would have heard radio waves.

The alternative is that civilizations don't last very long,

but destroy themselves.

CA: Professor Hawking, thank you for that answer.

We will take it as a salutary warning, I think,

for the rest of our conference this week.

Professor, we really thank you for the extraordinary effort you made

to share your questions with us today.

Thank you very much indeed.

(Applause)