Ask an astronomer what the universe is made of. He or she will describe stars and planets, giant clouds of gas and dust called nebulae and the variations and combinations of these, like star clusters, galaxies, black holes and quasars.
If your astronomer friend is fastidiously detailed, he or she will also mention all forms of electromagnetic radiation — radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays — and a collection of subatomic particles like neutrinos.
If you stop there, the astronomer will only be 20 percent correct.
All the matter made of electrons, protons and neutrons and all the known subatomic particles accounts only for 20 percent of the total matter in the universe.
The other 80 percent is made up of stuff that we have little understanding of, so little that we simply call it “dark matter.”
We can't see it.
It doesn't interact with ordinary matter in ways that we currently understand, but we know it's there because we can easily measure the effects of its gravitational pull on all the stuff that we can see.
According to a post at Technology Review's Physics arXiv blog, we're all getting popped by this stuff pretty regularly.
An average-sized human, a “70 kilogram lump of meat made largely of oxygen, hydrogen, carbon and nitrogen,” may get smacked quite often.
The researchers, Katherine Freese at the University of Michigan in Ann Arbor, and Christopher Savage at Stockholm University in Sweden, calculate that there may be some 100,000 hits per year for each human on the planet. That's about once every five minutes per person.
Freese and Savage don't make any claims about the health impact of all this dark matter slamming your body, most likely hitting the oxygen and hydrogen atoms. There is no rash of unexplained diseases or deaths that might be explained by dark matter interactions. But, there are health conditions that we don't understand.
Heck, maybe male pattern baldness should be renamed Dark Matter Pattern Baldness.
The eclipse begins at 7:30 p.m. Oklahoma time. While the maximum occurs after sunset for us, which is at 8:32 p.m. It's the best solar eclipse visible from Oklahoma in a long while.
Make sure you have proper eye protection!
I can't stress this enough. Sunglasses, even those with UV block, aren't safe. Neither is the mylar wrapping that some snack foods come in, no matter how many layers you use.
If you don't have any actual solar viewing material, use a large piece of cardboard with a small hole punched in it.
Let the sun shine through the hole onto a white sheet of paper. This “pinhole” projector will show a small but sharp image of the eclipsed sun.
Planet Visibility Report: Jupiter has disappeared into the sunset, but brilliant Venus remains as the “Evening Star” in the west after sunset, joined by Mars high in the south and Saturn in the east. The full moon of Saturday will be the closest and largest of the year. The new moon on the 20th creates the partial solar eclipse visible in late afternoon or early evening for Oklahomans.
Wayne Harris-Wyrick is director of the Kirkpatrick Planetarium at Science Museum Oklahoma. Questions or comments may be emailed to wwyrick@
View this month's star chart.