Hypothetically, how would you build a black hole?
How To Build A Star
Suppose you wanted to build a star. How would you go about making one?
What If Light Had No Speed Limit?
What would the universe be like if the speed of light were infinite?
Accentuate the Negative
There’s news on the web that cosmologists have proven the existence of negative mass. The news is based upon an article that recently appeared on the preprint arxiv, and has not yet been peer reviewed. The article in no way proves the existence of negative mass, but rather demonstrates the theoretical possibility of a form of negative mass within general relativity. In other words, it is an interesting “what if” paper rather than applied astrophysics.
Have You Heard the One About…
This week I’ve gotten a number of questions about various proposed models in astrophysics, such as the one about how anti-gravity could explain dark matter and dark energy. Or the one where dark matter is a result of quantum interference on a cosmic scale. Or the one where the cosmic microwave background is actually due to thermal turbulence rather than the big bang. There are lots of ideas that show up in the literature and in the press, so how do you judge the quality of a particular idea?
Of Cabbages and Kings
When talking about scientific ideas, you often hear terms such as theories, hypotheses, facts, laws, models, etc. Some of these terms are used in everyday speech, but with meanings other than their scientific ones. Someone might say they have a theory, when they really mean they have an idea. People talk about scientific laws as if they are facts, or use the phrase “just a theory” to distinguish it from some idealized truth. Even scientists will sometimes interchange terms like theory and law. We know what we mean, but we aren’t always precise with our usage. So what do these terms mean in a scientific sense?
In the Hole
The idea of a white hole as an anti-black hole sometimes gets mentioned, but white holes aren’t real. They are the result of taking the mathematics relativity beyond its usefulness.
Energy Matters
How do we know that dark energy isn’t due to some kind of repulsive matter? If we speculate on the effects of repulsive matter, we find that what we predict isn’t what we see. Whatever dark energy is, observational evidence shows it isn’t matter.