Comments Policy

"In the long run, we shape our lives, and we shape ourselves. The process never ends until we die. And the choices we make are ultimately our own responsibility." -Eleanor Roosevelt

I've always been a big fan of personal freedom, which includes the freedom to speak your mind, say what you think, ask questions, be wrong, and learn. This is, after all, how we've all improved ourselves over our lives, as none of us were born knowing all that we've managed to acquire over our lifetimes.

And I've never had to have an official comment policy for all the years I've been blogging; the most I've ever had to give was some gentle guidance many years ago. But as much as I both hate moderating comments and arguing on the internet, the time has come to address a growing problem that many of you have noticed: a few bad apples spoiling the comments section for the  bunch. So let's lay down what is and isn't okay here, and empower all of you to make this the forum and community you want it to be. For this page, therefore, the song can be nothing other than The Prodigy's

Smack My Bitch Up.

First off, I'm going to continue to disallow all the things I've disallowed in the past. The following things are completely off-limits on my blog, and will get you permanently banned:

  • Threats of harm -- physical or non-physical -- to any person or group of people.
  • Hate speech, including racist, sexist and anti-semitic speech, and especially including anything that can be construed as encouraging or inciting violence against a group of people.
  • Spam, including trying to promote your business or direct web traffic from the comments of this blog.

All of that is obvious to me, and that will continue to be enforced. But there's more to it than that: there's how we treat each other. On this blog, that means with our words to one another. Consider this image for a moment, if you will.

Image credit: Paul Graham of Graham's Hierarchy of Disagreement.

We all say things -- sometimes quite confidently -- that turn out to be wrong. It's not surprising: we are limited in how much information we have, in our experiences, and in how we've put it all together. This is simultaneously one of the best things about science, because it's always learning and always self-correcting, and also one of the hardest things about being a scientifically-minded and kind human, because we both are sometimes wrong and need to change our worldview in order to be consistent, and also because when others need to be corrected, we want to set them on the right course.

I will always encourage everyone, when faced with the last of those tasks, to work from as high up on the pyramid as is possible. And believe me, I know it's hard, particularly when you feel like the following is in order:

...because sometimes people *deserve* this. 

Which -- I'm not going to lie -- sometimes is in order.

Because sometimes, arguments are not genuine.

Sometimes, people leave comments and state opinions for reasons other than to honestly attempt to learn, educate, or otherwise exchange information.

And when that happens here, it can hijack a very good community that is committed to sharing what we know about the Universe and how we know it, and turn the comments section into an indecipherable mess.

King of the Hill once covered this very well, IMO.

I've been very, very patient with giving people the benefit of the doubt. Some people do come here curious about the Universe, but with some very deep misconceptions about how things work. People with this mindset are often willing to change their minds if the right evidence comes along. I (sometimes naïvely) initially think that everyone who comes here is like this, particularly when a comment or question appears on a relevant post.

For example, when talking about how we know that the Earth moves.

Image credit: Richard Helmich.

There are plenty of hints that show us the Earth is rotating, but -- from the perspective of an observer on Earth -- it is completely indistinguishable whether it is the Earth that rotates on its axis every 24 hours or whether the entire Universe and everything in it rotates ones every 24 hours around the Earth. That much is true.

However, these two perspectives are not equivalent for everything else in the Universe. Every naked-eye star in the night sky -- including Polaris, by the way -- would be breaking the speed of light if they were moving around the Earth. The slowing of the Earth's rotation -- due to the frictional torque of the Sun-Moon-Earth system -- would not exist, and thus there would be no explanation for the gradual but measurable changes in the length of the day. And, on cosmological scales, a rotating Universe (which is an interesting toy model) is constrained to be less than one rotation of the Universe about any axis over the entire history of the Universe.

And that is what I'd consider a fair explanation. At this point, the reasonable person may have follow-up questions, but would presumably have been confronted with evidence they didn't consider, and the discussion would evolve. But the unreasonable person would shift the goalposts, bring up a new argument, point to some misinterpreted piece of evidence, etc., in some never-ending game of cat-and-mouse.

I feel like that's what's been going on in the comments of this blog, and that ends now.

Image credit: found at

Because from here on out, you are no longer free to promote your own, personal, anti-scientific screed here. Not on this blog, not on any old posts, not on any new posts. It's wrong, it's distracting, it's deleterious to the community and it's damaging to the good people who come here for the same purposes I do: to share the story of what we know about the Universe and how we know it with one another.

From here on out -- and I'd encourage the honest attempt before doing this -- you can send the offending commenter here, to this page. This page is -- I hereby declare -- the only place on Starts With A Bang where scientifically disingenuous comments are not going to be deleted immediately. If you said your piece of mind and were properly informed, and you continue to plow ahead and promote your anti-scientific nonsense, you get one warning to take it to this page.

That is what I need you, my readers, to do: if you catch someone doing this, warn them to either cut it out or take it here, and if you warn them, and they violate this policy, I will contact them personally, and -- if necessary -- ban them.

And I'm telling everyone right now, because I want to be very, very clear:

I don't want to have to ban anybody!

You are free to speak however you like, but you are responsible for what you say. Your speech is your privilege here, so respect the blog, respect your community, and respect yourself with how you use it.

If you want to know the answer to a science question, we've got a great community here that can help you. If you want to know why the large-scale structure simulation, above, isn't expanding, ask that. You'll likely be told the correct answer: the simulation is done in an expanding Universe, but the expansion is scaled out of the visual end-product, because it's not very interesting to watch a simulation containing 1 billion particles to only have 80 particles by the end of it, because the volume of the Universe has expanded by a factor of 12 million over the course of the simulation.

All structure formation simulations (including the beautiful cluster-formation one, below) do this when they're presented visually; this is well-known and taken into account. I should know, it's my area of expertise!

So let's treat each other, ourselves, and our community with respect. If you can't let go of your idea even after it's been explained to you, you will be told to take it here, where you may or may not get a response, but you will not clutter up the rest of the blog with it, or you will no longer be allowed to comment here. This is a free and open forum with very few rules, so don't abuse them and we'll all have a better place to spend time together.

More like this

Would everyone who can offer some insight comment to who George Lemaitre is. I have researched it and I have his one book "A Day Without Yesterday". What I seem to find odd/interesting is that because he was a priest he seems to be shunned by the scientific community. If you see pictures of him (even discussing the singularity beginning event) with Albert Einstein it does seem an odd yet interesting wonder. I do know that he is sometimes considered the "Father of the Big Bang" nomenclature but is was really Fred Hoyle who coined the phrase as a slang and derisive term against Lemaitre. From what I can gather (not totally found in print) Fred Hoyle did a radio broadcast and while Lemaitre had called the event a "Primordial Atom" or "Cosmic Egg" Hoyle reiterated something like the following; 'Oh George; you mean the beginning was like a big bang?" and POOF. That is how we got the term "Big Bang". That term stuck in the minds of us feeble humans and Lemaitre's term and he got cast into the dustbin of history. Frankly, that bothers me...regardless of the white collar, Lemaitre was a cosmologist and MIT grad and physicist. Comments?

Opps, I think I posted this in the wrong spot. Now what do I do??

Just post it in the right one and you'll be golden.

So, if anyone here has any expertise in 'virtual particles', portals, Coulombs, Casimir etc. I'd appreciate other insights and background for the Casimir - Coulomb post.

By Ed Ward, MD (not verified) on 15 Nov 2013 #permalink

When measuring cosmic distance using redshift, is accelerating expansion taken into account, and does it make a difference?

Hi Ethan, I would like to run your RSS feed in a widget on WI Astronomy
WI Astronomy is a Space and Astronomy News public outreach website.
Tom Grzadzielewski
W I Astronomy

By Tom Grzadzielewski (not verified) on 28 Nov 2014 #permalink

Periodically I ask myself what is the universe. Is there anything else. Now I wonder how Ethan would answer that question.

@Mike #5 (from ten months ago): Yes, it is. Take a look at some of Ethan's posts which specifically deal with dark energy. You'll usually find a plot which shows the computed age of the Universe as a function of the expansion history. That is done by integrating how the scale factor (like the expansion rate) varies as a function of cosmic time.

By Michael Kelsey (not verified) on 01 Feb 2015 #permalink

Dear Ethan,

During the heavy bombardment period, how often was earth hit? Once a day, week, year?


By Greg McMahan (not verified) on 28 May 2016 #permalink

On October 27, 2010 you posted an article, "How Big is the Unobservable Universe", in which you claim the universe is FLAT after inflation. But FLAT implies an infinite plane or hyperplane, which is not possible in finite time (of inflation, or any other process). Is this not an error on your part? Thank you. FB

By Frank Bennett (not verified) on 12 Jun 2017 #permalink


I think you asked a really good question but to the wrong part of this website. You should repost to Questions-Suggestions page.

I also thought about this not making sense. My personal view is that Universe is actually curved uniformly like a surface of a sphere so that Universal curvature is not directly detectable by observers inside of it.
I think similar to surface of a sphere which is a 2d space bent in 3rd space dimension, Universe could be 3d space bent in time dimension.
More detail from me if you like:

@Franks #11 and #12: For a three-dimensional space, "flat" does not have to imply an infinite cartesian space. It means that the space has zero net curvature.

This can mean zero curvature in every direction, or it can mean positive curvature in some directions and negative curvature in others, or it can mean positive curvature in some regions and negative in others, which add up to a global zero.

A two-dimensional non-trivial example is the surface of a torus. The torus has negative curvature on the portion of the surface near the hole, positive curvature on the portion of the surface away from the hole, and zero curvature along the circles where those regions meet. If you work through the math, the _net_ curvature for the whole space (two dimensional finite surface) is zero.

Similarly, it is possible for our universe to _not_ be an infinite Cartesian grid, but still be globally flat.

By Michael Kelsey (not verified) on 13 Jun 2017 #permalink

Are all photos of the galaxies fake by Hubble?

what If the inflation was not happened?

My English is not good but I will tell my point. You are telling that there is something other than nothing right. I agree with you and my theory is
1. That universe is filled with some kind of liquid.
2. Think of a balloon. If you put a hole in the balloon the air inside the balloon is mixed with the atmosphere.
3. If you put a balloon inside a water tank and burst it the air in the balloon quickly get to atmosphere. If any solid object is submerged it will fall slowly according to is weight.
4. Now in space if you put a solid object it will float. But if there is any leak in the air where does it goes ?
5. What is sucking the air from the spaceship ?
6. The air the space are going to the atmosphere that we don't know.
7. Like I said the air going out from the liquid that soround the space.
8. Maybe we are falling down in the liquid that we cannot see.
I think you will understand my theory but I didn't know much about universe but it is what I think. I mean is there any other explanations.
I didn't know much about universe. Please let me know if you find anything from my theory.
Email me if you like my theory.

By Madhankumar (not verified) on 31 Aug 2017 #permalink


Let me try this point by point:

1. There is no evidence that the universe is filled with a liquid. Liquids are made of atoms or molecules. We can easily detect these. We have not detected them in any quantity in space, therefore there is no liquid filling space.

2. True, but irrelevant. If you put a hole in a balloon ANYWHERE, the gas will leak out. It's simply a matter of higher gas pressure inside the balloon than outside.

3. Again true, but irrelevant. Air is less dense than water. It will experience a buoyant force causing it to rise to the surface of the water. Solids can be either more or less dense than water. Those that are less dense will experience a buoyant force that is greater than their weight; i.e. they float. Those more dense will experience a buoyant force as well, but their weight is greater, so they sink.

4. Not true at all. In no sense can it be said that a solid object floats in space. A solid object in space moves along a geodesic path that is determined by the local gravitational field. This may be zero, so that the object does not move, but the object doesn't float. As soon as you act upon that solid object with ANY force, it will be accelerated.

5. There is no such thing as "sucking". What happens is simply gas moving from a high pressure container to a low pressure container, in accordance with the second law of thermodynamics.

6,7. Both are unclear. What exactly do you mean? "The air the space are going to the atmosphere"??? Do you mean that air from the atmosphere escapes into space? Sure, it does, but again irrelevant. Again it's a matter of balance of forces; the atmosphere is at higher pressure than the surrounding space (essentially at zero pressure). The air is held by gravity, but tends to escape because of pressure differential. If gravity were weaker, we would have a lower pressure atmosphere (see Mars for example). If our gravity were stronger, like Jupiter's, our atmosphere would have higher pressure.

8. Again, there's no such thing as liquid we cannot "see", at least if we substitute the word "observe". A liquid may be transparent, but it still is matter. We can weigh it, measure its pressure, etc. Space is not filled with any liquid.