Q 01/05

Dark matter is so called because it does not interact with what?

A) Ordinary matter of any kind at all

B) Gravity or any other known force

C) Electromagnetic radiation such as light

D) The strong and weak nuclear forces

Answer · why

C) Electromagnetic radiation such as light

Its existence is inferred entirely from gravitational effects.

Q 02/05

In the standard Lambda-CDM model, roughly what share of the universe's mass-energy is dark matter?

A) 27%

B) 45%

C) 60%

D) 68%

Answer · why

A) 27%

Ordinary matter is about 5 percent and dark energy about 68 percent.

Q 03/05

Dark matter makes up roughly what fraction of the total matter (not energy) in the universe?

A) 15%

B) 50%

C) 85%

D) 99%

Answer · why

C) 85%

Ordinary atoms account for the remaining 15 percent or so.

Q 04/05

According to the article, all the dark matter out to Neptune's orbit would weigh about as much as what?

A) The Moon

B) A large asteroid

C) A grain of sand

D) The Earth

Answer · why

B) A large asteroid

Its density in the Solar System is far lower than that of ordinary matter.

Q 05/05

Which physicist speculated in 1884 that many stars near the Sun might be dark bodies?

A) James Clerk Maxwell

B) Ernest Rutherford

C) Isaac Newton

D) Lord Kelvin

Answer · why

D) Lord Kelvin

He was estimating the density of stars from their velocity dispersion.