Five questions no one can answer

Science doesn't have all the answers. But it has the ones you can trust.

Users on reddithave been compiling the questions science is still to answer.

It's worth remembering that no science claims to be the definitive answer to anything. Proclaiming the 'one truth' is the hallmark of faith, not evidence based reasoning.

Any scientific study, or reasoning, is only the answer based on what's known so far.

Nevertheless, reddit users had some questions they'd like a little more clarity on already:

1. Are we alone in the universe?

The odds are, given the vast size of the universe, and the infinite number of celestial bodies flying around and infinite number of solar systems, we are not alone.

Yet so far we've not found any.

It's possible that Earth is the first life in the universe, after all it has to began somewhere.

Or we could be the last.

It has been covered, sort of, by the Fermi paradox:

2. Why do placebos work?

Taking drugs that don't work, to make you better.

Is it proof your symptoms were just psychosomatic or stress related?

Even physical pain can be relieved by something which later turns out not to be a painkiller.

3. Why do humans dream?

In 1953 two scientists observed a correlation between 'rapid eye movement' (REM) sleep and having vivid, memorable dreams.

In subsequent years, REM sleep brain activity was found to be similar to waking brain activity, suggesting REM sleep is no sleep at all.

A 1960 study found that interrupting REM sleep made subjects tense and irritable, suggesting we may need dreams to help us relax and process our worries.

A definitive answer on this remains elusive.

4. What's on the other side of a black hole?

This particular problem is addressed in Andre Deutsch's book The Biggest Questions in Science.

Writing for the Guardian, Deutsch suggested that he problem with theories about black holes, and much of physics, is the disconnect between Albert Einstein's theory of relatively and quantum physics.

According to Einstein, a black hole will eventually collapse on it itself, creating singularity. Quantum physics doesn't allow for this, or black holes at all really.

Speaking on this Science podcast for Space.com, theoretical physicist at Princeton University Edward Witten explained:

What you get from classical general relativity, and also what everyone understands about a black hole, is that it can absorb anything that comes near, but it can't emit anything.

But quantum mechanics doesn't allow such an object to exist.

The incompatibly of these branches of science, mean we don't have the tools to find the answer about black holes.

5. How does gravity work?

We know that the more mass something has, the more it can attract objects into its orbit.

As to why, there's no real answer.

It's not clear what holds atoms together when that force seems different to gravity.

What even is gravity - is it a particle?

The problem of gravity in physics, plays a role in the black hole problem.

HT National Sleep Foundation, Guardian, IFL Science

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