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Why Science Will Never Know Everything About Our Universe

“The Universe itself may be finite or may be infinite; the jury is still out. But one thing is certain: the part that’s accessible to us is finite. Even with the expanding Universe, even with all the galaxies and stars and planet and molecules and atoms and subatomic particles in it, there’s only so much we can access. And those limitations – the total numbers of particles and the total amount of energy available in the Universe – means there’s only a finite amount of information we can determine about our cosmos. For the first time, we can quantify that, and begin to infer which things we might never understand.”

As we peel back the layers of information deeper and deeper into the Universe’s history, we uncover progressively more knowledge about how everything we know today came to be. The discovery of distant galaxies and their redshifts led to expanding Universe, which led to the Big Bang and the discovery of very early phases like the cosmic microwave background and big bang nucleosynthesis. But before that, there was a period of cosmic inflation that left its mark on the Universe. What came before inflation, then? Did it always exist? Did it have a beginning? Or did it mark the rebirth of a cosmic cycle? Maddeningly, this information may forever be inaccessible to us, as the nature of inflation wipes all this information clean from our visible Universe.

Go find out why some things are inherently unknowable on this special edition of Starts With A Bang!

The Paradoxes That Threaten To Tear Modern Cosmology Apart

Some simple observations about the universe seem to contradict basic physics. Solving these paradoxes could change the way we think about the cosmos

Revolutions in science often come from the study of seemingly unresolvable paradoxes. An intense focus on these paradoxes, and their eventual resolution, is a process that has leads to many important breakthroughs.

So an interesting exercise is to list the paradoxes associated with current ideas in science. It’s just possible that these paradoxes will lead to the next generation of ideas about the universe.

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Ask Ethan: How can we see so far away in such a young Universe?

“How can we look at a segment of space 92 Billion miles across when light from each edge only had 13.7 billion years to travel? Even assuming you mean those points would have moved away farther during the travel time and we are calculating where they would be rather than what we see, and include that at that distance space can be expanding faster than c, the numbers still seem high.”

Look out at a nearby object in our Universe, and you’ll find that the amount of time you look back (in years) is pretty much exactly equal to the object’s distance (in light years). But look far away, and these two numbers start to diverge. In our 13.8 billion year old Universe, in fact, we can see back up to 46 billion light years in any direction. If you think this number seems absurd, you’re not alone. If the Universe were full of material everywhere and that material emitted light that was limited by c, you’d only be able to see for 13.8 billion light years. If you added in that the material could also be moving away from you at up to c, perhaps it could reach twice that: 27.6 billion light years. Yet the figure we have, 46 billion light years, only comes about because the fabric of space itself is stretching, a unique property of general relativity.

Come find out the whole, remarkable story of how this happens and how we know on this week’s Ask Ethan!

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Physicists must accept that some things are unknowable

“What we’re left with is an observable Universe that’s huge: 46 billion light years in radius, containing some 10^12 galaxies, 10^24 stars, 10^80 atoms and nearly 10^90 photons. But those numbers, while astronomical, are finite, and don’t give us any information about what happened in the Universe prior to the last tiny-fraction-of-a-second of inflation. We can do theoretical calculations to attempt to gain some insight, but they’re all model dependent. With the exception of a few specific models that would leave observable traces in our Universe (most don’t), we have no way of knowing how — or even if — the Universe got its start.”

As we peel back the layers of information deeper and deeper into the Universe’s history, we uncover progressively more knowledge about how everything we know today came to be. The discovery of distant galaxies and their redshifts led to expanding Universe, which led to the Big Bang and the discovery of very early phases like the cosmic microwave background and big bang nucleosynthesis. But before that, there was a period of cosmic inflation that left its mark on the Universe. What came before inflation, then? Did it always exist? Did it have a beginning? Or did it mark the rebirth of a cosmic cycle? Maddeningly, this information may forever be inaccessible to us, as the nature of inflation wipes all this information clean from our visible Universe.

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Even Cosmic Distances Need To Be Adjusted For Inflation

“The light from EGS-zs8–1 comes to us from some 13.1 billion years ago, from when the Universe was a mere 660 million years old. But here’s the kicker: when we calculate the distance to this galaxy, we find it to be 29 billion light years away. In other words, not only is this galaxy farther away than the Universe’s age, it’s much farther away!”

If you’ve ever wondered about the great cosmic distances in our Universe, check out my latest for Forbes!