NASA | Using Quasars to Measure the Earth: A Brief History of VLBI - 3D

The video explains how the Earth's ground moves and wobbles on its axis, affecting the length of a day. Scientists use a technique called Very Long Baseline Interferometry (VLBI) to measure these movements precisely. Originally developed to take pictures of quasars, VLBI uses radio waves emitted by quasars to determine the relative movement of telescopes. By analyzing the time differences in wave reception, scientists can calculate the distance between telescopes and observe the Earth's movements. This technique helps understand the Earth's orientation and its subtle changes over time.

What is a common misconception about the Earth's movement?

• The Earth only moves during earthquakes.

• Days are exactly 24 hours long.

• The Earth does not rotate at all.

• The Earth rotates in a square pattern.

What does VLBI stand for?

• Variable Long Baseline Interferometry

• Very Large Baseline Interferometry

• Variable Length Baseline Interferometry

• Very Long Baseline Interferometry

What was the original purpose of developing VLBI?

• To measure the Earth's rotation

• To measure the distance between planets

• To take pictures of quasars

• To study earthquakes

How does VLBI help in understanding Earth's movements?

• By calculating the speed of light

• By observing time differences in radio waves from quasars

• By analyzing the color of quasars

• By measuring the distance between stars

What can VLBI reveal about the ground beneath telescopes?

• It moves around slightly

• It becomes transparent

• It remains completely still

• It changes color