According to one astrophysicist, gravity can exist even without mass, suggesting no need for the elusive substance -- Dark Matter.
Gravity Can Exist Without Mass
In a new study, astrophysicist Richard Lieu at the University of Alabama in Huntsville has proposed that the Universe may have thin, shell-like layers of "topological defects" that give rise to gravity without any underlying mass instead of dark matter binding galaxies and other entities together.
Lieu's first goal was to discover an alternative solution to the Einstein field equations, which establish a relationship between space-time curvature and the existence of matter in it.
According to Einstein's 1915 general theory of relativity, space-time warps around matter bundles and radiation streams in the Universe based on their energy and momentum. Naturally, that energy and mass are connected in Einstein's well-known equation, E=mc2.
Thus, an item's mass is related to its energy, which causes space-time to bend. Einstein defined gravity as this curvature of space-time, a step from Newton's 17th-century approximation of gravity as a force between two mass-containing objects. Stated differently, gravity appears to be closely related to mass.
Not at all, asserts Lieu. To account for a finite gravitational force in the absence of any observable mass, Lieu began by simplifying the Einstein field equations. He claims his efforts were driven by his frustration with the status quo, including the notion of dark matter's existence despite the lack of direct evidence.
Lieu's solution comprises shell-shaped topological defects that could arise in extremely densely populated, highly condensed space areas.
A small layer of positive mass is nestled inside an outer layer of negative mass in these sets of concentric shells. The total mass of the two layers is precisely zero since the two masses cancel each other out. However, a star atop this shell feels a strong gravitational pull that pulls it toward the center of the shell.
According to Lieu, the paper's thesis is that, at the very least, the shells it proposes are massless. There's no reason to continue this seemingly never-ending hunt for dark matter if those controversial ideas are any indication.
Gravity and Mass
Gravity is the force that pulls items toward the center of a planet or other entity. Every planet orbiting the Sun is held in place by gravity.
Things fall and land on the ground due to gravity. When you jump, you land on the ground for the same reason -- gravity. This invisible force pulls objects toward each other and keeps you on the ground instead of floating.
Gravity is inherent in anything that has mass. It increases with object mass and becomes less strong with distance. Therefore, an object's gravitational force is stronger the closer it is to another object.
All of Earth's mass contributes to its gravity. Your entire body is subject to a cumulative gravitational force from its mass. It is the source of your weight. Furthermore, your weight would be lower on a planet with less mass than Earth.
The moon's orbit around Earth and the planets' orbits around the Sun are maintained by gravity. Ocean tides result from the seas being drawn towards the moon by its gravitational attraction. Planets and stars are formed by gravity, drawing their constituent materials together.
Light is also drawn toward matter by gravity. It was Albert Einstein who discovered this idea.
If you beam a flashlight, gravity will draw the light upward, making it noticeably redder. Although the alteration is invisible to the human eye, scientists can measure it. Black holes' gravitational pull is excellent because they contain so much mass in such a short space that nothing can escape, even light.
RELATED ARTICLE : What's The Shape Of The Universe? Experts Say It Could Be A 3-D Donut!
Check out more news and information on Space in Science Times.
