Answer:
b. flat rotation curves in spiral galaxies
Explanation:
Dark matter accounts for majority of the matter in the universe (about 85%). It is considered to be composed of subatomic particles which are yet to be discovered. Dark matter cannot be observed because it does not emit light that can be detected. Only its gravitational effect is visible.
Astronomers when calculated the mass of the visible matter and tried to account for the observed speed of stars in the galaxy, there was a mismatch. To understand what caused this mismatch, astronomers gave name to the invisible matter as the Dark Matter.
The expected velocity of stars should decrease away from the near the center of the galaxy but a constant velocity of stars was observed that is a relatively flat rotation curve was obtained.
Thus, flat rotation curves in spiral galaxies in an evidence of Dark Matter.
Answer:
Explanation:
Mực nước biển dâng cao, nhiều lục địa lớn nhất dần dần bị nhấn chìm, hiện tượng tan băng còn giải phóng nhiều loại virus cổ đại nguy hiểm, các hoạt động khai thác trên biển của con người gặp khó khăn
Answer:
The drawbacks of regionalism include the possibility for each individual city or county to lose their respective independence and/or identity.
The firing on Fort Sumter on April 12, 1861, was the first armed conflict of the <u>Civil War.</u>
