Category: universe

Aliens In The Multiverse? Here’s Why Dar…

Aliens In The Multiverse? Here’s Why Dark Energy Doesn’t Tell You Anything

“It’s important to recognize that there are a wide variety of possible values that dark energy could have, including significantly larger values, that would still lead to a Universe very much like our own. Until we understand where these values come from, and what makes one set of values more likely than another, it’s grossly unfair to claim that we won the cosmic lottery in having a Universe with the values ours possesses. Unless you know the rules that govern the game you’re playing, you have no idea how likely or unlikely the one result you see actually was.”

There are a series of interesting results that have just emerged from the EAGLE collaboration, which has been simulating the Universe to learn what types of stars and galaxies form within it. They varied the value of dark energy in it tremendously, and found that even if you increased the amount by five, ten, or fifty times as much, you’d still form plenty of stars and galaxies: enough to give you chances at life like we have here. This surprised them, since they assumed the value of dark energy we have is finely-tuned to allow life. But it appears that things may not be as finely-tuned as we had thought! The simulation results are interesting, but this doesn’t really tell you anything about aliens in the Multiverse, since we have no idea what causes dark energy to have the values that it does.

Until we know the rules that govern this, we can’t really say what dark energy tells us about aliens in Universes other than our own. Here’s why.

Ask Ethan: How Many Galaxies Have Already Disa…

Ask Ethan: How Many Galaxies Have Already Disappeared From Our Perspective?

“So how many earth observable galaxies have dropped out of sight? That is, how many galaxies (with the highest redshift) have disappeared from our point of view?”

When we look out at the distant reaches of space, there are some 2 trillion galaxies observable within our Universe. But our Universe is expanding, the expansion is accelerating, and light can only travel at the speed of light. Does that mean that galaxies are dropping out of sight?

There are two ways to look at this: from the point of view of not being able to see galaxies that we can presently see, and from the point of view of whether we can see the light those galaxies are emitting today, 13.8 billion years after the Big Bang? If we take the first definition, not only is the answer “zero,” but there will be trillions more galaxies revealed to us over time. But if we take the second, we find that most of the galaxies we can see today are already gone.

How many galaxies have already disappeared from our perspective? The cosmic implications should motivate us to get out there and explore while there’s still some good Universe left to go and see!

Earth’s rotation is slowing slightly with time

Earth’s rotation is slowing slightly with time:

“In the year 1820, a rotation took exactly 24 hours, or 86,400
standard seconds. Since 1820, the mean solar day has increased by about
2.5 milliseconds.”

“At the time of the dinosaurs, Earth completed one rotation in
about 23 hours,” says MacMillan, who is a member of the VLBI team at
NASA Goddard.

* How can the moon slow down the earth ?

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Are the heavens moving or are we?

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In the previous series of posts, we discussed about the key role that a rotating earth plays in space shuttle launches and quickly skimmed through why the earth began to rotate in the first place.

But in the 21st century, there are many experiments  (Coriolis effect,  Foucault’s pendulum ,etc, etc) that you can do to convince yourself that the Earth is indeed rotating.

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                                             ISS Live Stream

But back in the days of Galileo it was still debatable whether Earth was rotating or not. 

Why does a ball thrown straight up in the air fall to the same place on the ground ?

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One
of the profound Aristotelian arguments against the rotation of the
Earth was that if the Earth were rotating, a thrown ball/arrow would not
land in the same place that it was thrown.

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This was believed so
because, by the time the projectile traverses its path the Earth would
have moved by a certain distance. Hence, the ball would never land at
the same place it was thrown.

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Take a second to think about this. Can you come up with an argument against this rationale ?

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Here
is an excellent argument given by Galileo in favor of the rotation of
the Earth and why things would still fall to the same place even if the
Earth were rotating:

In replying to this, those who make the earth movable answer that the canon and the ball which are on the earth share its motion or rather that all of them together have the same motion naturally.

Therefore the ball does not start from rest at all but to its motion about the center joins one of projection upward which neither removes not impedes the former.

You
will see the same thing by making the experiment on a ship with a ball
thrown perpendicularly upward from a catapult. It will return to the
same place whether the ship is moving or standing still

The profundity of this argument is that, the very same principle that ‘ball does not start from rest at all  but with velocity of the earth’ is used by space shuttles to reach orbital velocity with lesser fuel consumption.

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But despite Galileo’s argument, it was still believed for a long time that it were the heavens that moved and not the earth.

For
God hath established the world which shall not be moved in spite of
contrary reasons because they are clearly not conclusive persuasions.

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Why did the Earth start spinning?

We have been discussing about the rotation of the Earth in the past couple of posts but lets take a second to understand why the earth is rotating in the first place.

Here is a quick summary:

Our Solar System formed about 4.6 billion years ago when a huge cloud
of gas and dust started to collapse under its own gravity.

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As the cloud collapsed, it started to spin. Some of the material
within this cloud gathered into swirling eddies and eventually formed
into planets. As the planets formed, they kept this spinning motion.

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As material gathered in more closely to form a planet, like Earth, the
material spun faster. This is similar to what you see when skaters pull in their arms and spin
faster.

And as a result since there are no forces are acting on Earth to slow it down, it continues to spin to this day. **

** not entirely true as we shall explore soon

Previous posts:

The shape of the Earth is an oblate spheroid: A visual demo

How does earth’s rotation affect space shuttle launches ?

Ask Ethan: How Big Will The Universe Get? “Th…

Ask Ethan: How Big Will The Universe Get?

“The current estimate for the diameter of the universe is 93 billion light years. With the current acceleration of the universe measured by redshift, and the future exponential acceleration, how long until “we” hit a diameter of 100 billion light years?”

Our Universe is made up of a number of different types of energy, including dark energy, dark matter, normal matter, neutrinos, and radiation. When you combine those different forms of energy with our observed expansion rate, you arrive at a Universe prediction for how the Universe expanded in the past and how it will continue to expand into the future. As distant galaxies accelerate away from us, we can make predictions for how large our observable Universe will get as time goes on. At present, our visible Universe is 92 billion light years in diameter, with an age of 13.8 billion years. When will we hit 100 billion light years? Or a trillion? Or a quadrillion?

The answer is straightforward, fun, and profound. Come find out how big the Universe will get, and how fast it will get there, on this week’s Ask Ethan!

Hubble’s Greatest Discoveries Weren&rsqu…

Hubble’s Greatest Discoveries Weren’t Planned; They Were Surprises

“And if we head out beyond our own galaxy, that’s where Hubble truly shines, having taught us more about the Universe than we ever imagined was out there. One of the greatest, most ambitious projects ever undertaken came in the mid-1990s, when astronomers in charge of Hubble redefined staring into the unknown. It was possibly the bravest thing ever done with the Hubble Space Telescope: to find a patch of sky with absolutely nothing in it — no bright stars, no nebulae, and no known galaxies — and observe it. Not just for a few minutes, or an hour, or even for a day. But orbit-after-orbit, for a huge amount of time, staring off into the nothingness of empty space, recording image after image of pure darkness.

What came back was amazing. Beyond what we could see, there were thousands upon thousand of galaxies out there in the abyss of space, in a tiny region of sky.”

28 years ago today, the Hubble Space Telescope was deployed. Since that time, it’s changed our view of the Solar System, the stars, nebulae, galaxies, and the entire Universe. But here’s the kicker: almost all of what it discovered wasn’t what it was designed to look for. We were able to learn so much from Hubble because it broke through the next frontier, looking at the Universe in a way we’ve never looked at it before. Astronomers and astrophysicists found clever ways to exploit its capabilities, and the observatory itself was overbuilt to the point where, 28 years later, it’s still one of the most sought-after telescopes as far as observing time goes.

Hubble’s greatest discoveries weren’t planned, but the planning we did enabled them to become real. Here are some great reasons to celebrate its anniversary.

The Most Important Equation In The Universe &…

The Most Important Equation In The Universe

“The first Friedmann equation describes how, based on what is in the universe, its expansion rate will change over time. If you want to know where the Universe came from and where it’s headed, all you need to measure is how it is expanding today and what is in it. This equation allows you to predict the rest!”

In 1915, Einstein put forth General Relativity as a new theory of gravity. It reproduced all of Newton’s earlier successes, solved the problem that Newton couldn’t of Mercury’s orbit, and made a new prediction of bent starlight by large masses, verified during the 1919 solar eclipse. Despite the fact that it included a cosmological constant to keep the Universe static, that didn’t deter Soviet physicist Alexander Friedmann from solving Einstein’s equations for a Universe that was filled with matter and energy, all the way back in 1922. The two generic equations he found, known as the Friedmann equations, immediately related measurable quantities like the amount of matter in the Universe to the expansion or contraction rate, which just years later became validated by Hubble’s observations. But the young Friedmann never lived to see it; he died of typhoid fever contracted when he was returning from his honeymoon in 1925.

Nearly 100 years later, it still stands as the equation that determines the history and fate of the Universe. Come see why I call it the most important equation in the Universe!

One Galaxy Cluster, Through Hubble’s E…

One Galaxy Cluster, Through Hubble’s Eyes, Can Show Us The Entire Universe

“There’s more gravity than the gas can provide, showing the presence of non-baryonic dark matter.

But all the mass, combined, contributes to gravitational lensing.

The bending of space stretches and magnifies the light from galaxies behind the cluster.

This is the whole purpose of the joint Hubble/Spitzer RELICS program, highlighted by this galaxy cluster.”

Want to see the most distant galaxy in the Universe? You don’t simply need the world’s greatest telescopes; you also need an assist from gravity. Galaxy clusters provide the largest gravitational sources in the Universe, thereby providing the largest natural magnification enhancements through gravitational lensing. While the internal dynamics of the galaxies tell us that there must be dark matter present, and that dark matter is something other than normal (atom-based) matter, the overall gravitational effects enhance any telescope-based views of the Universe. The joint Hubble/Spitzer RELICS program is imaging 41 of these massive galaxy clusters, hoping to magnify ultra-distant galaxies more distant than any we’ve ever seen before. When the James Webb Space Telescope comes online, these will be the places where our greatest target candidates for “most distant galaxy in the Universe” will come from.

The next step of our great cosmic journey is beginning right now. Come get a glimpse of the future for yourself!

Ask Ethan: How Will Our Universe End? “When w…

Ask Ethan: How Will Our Universe End?

“When will our universe reach the point of maximum entropy? And what other possibilities exist for our universe in the far future?”

It’s nearly 14 billion years since the hot Big Bang gave rise to our observable Universe, which now consists of some 2 trillion galaxies spread out across a sphere over 46 billion light years in radius. But despite how plentiful the matter in our Universe is, it won’t last forever. The stars will all burn out, and even the new stars that form will eventually run out of gas to form from. Dark energy will drive the unbound galaxies away, while gravitation will pull the bound ones into a single structure. Over time, ejections and mergers occur, littering the Universe with isolated masses and setting up enormous black holes embedded in dark matter halos as the last remnants of galaxies. After enough time passes, the final black holes decay, leaving only low-energy, ultra-high-entropy radiation behind.

It will take a long time, but this is the ultimate fate of everything in the far future of the Universe!