I just saw this thread: Parallel tangents and curves and there were discussions in it on whether or not it was appropriate to downvote an answer which was fully worked out for a questioner who seemed to do no more than post a homework question without thought/etc. I'm new here and don't have a h...

We all know that mostly stars are at the center of planetary systems, but is it possible that instead of star there was a rocky planet in the center with stars (and other planets and moons) orbiting it? To be more concrete: Is it possible for a star to have the same mass and radius as e.g. the M...

Things are not empty space. Our classical intuition fails at the quantum level. Matter does not pass through other matter mainly due to the Pauli exclusion principle and due to the electromagnetic repulsion of the electrons. The closer you bring two atoms, i.e. the more the areas of non-zero exp...

The problem is what Konstantin Tsiolkovsky discovered 100 years ago: as speed increases, the mass required (in fuel) increases exponentially. This relation, specifically, is $$ \Delta v=v_e\ln\left(\frac{m_i}{m_f}\right) $$ where $v_e$ is the exhaust velocity, $m_i$ the initial mass and $m_f$ the...

The truth is we don't know. But when you think about it, how can we know? If we knew what technology would eventually come out of experiments like this, why would we not build that technology now? Large expensive machines like the CERN super-collider help us to further understand that laws of na...

TL;DR: This answer arrives at roughly the same conclusion as Kyle Kanos', i.e. in addition to payload considerations, the difficulty lies in stuffing a small rocket with a mass of fuel exceeding to the mass of the rocket itself. This answer, however, is more rigorous in how the $\Delta v$ budget ...

The electromagnetic spectrum covers a wide range of values: (source) What we see is visible light (just right of the middle of the page), which is a very small section of the spectrum. If the light source emits brightly in the infrared, our eyes will not be able to see it. As an example, consi...

I noticed there are quite a few questions about the Populist badge. Some people are confused about its purpose, or upset about its existence, yet others simply wonder why they didn't get theirs. I just want to change the Populist Badge's description from: Highest scoring answer that outscore...

I was reviewing First Posts just now, and I received the following message after my 20th vote: Thank you for reviewing 20 First Posts today; come back in 8 hours to continue reviewing. I see other users, with far lower reputation than me, voting up to 40 times per day. Why is it I only hav...

So I did what I thought was my 40 reviews in the Close Vote Review Queue today. However, when I went to see about reviewing other queues, I noticed the message for the Close Votes said, "Thank you for reviewing 20 close votes today" instead of saying the normal 40. I went and counted my close vot...