Final answer:
Solar radiation did not significantly contribute to the Earth's early molten state, while geothermal energy, radioactive decay, and tidal forces did.
Step-by-step explanation:
The source of heat that did not significantly contribute to the Earth's early molten state is solar radiation. The major contributors to this molten state were geothermal energy, which originates from the Earth's core and radioactive decay of elements in the crust, and tidal forces due to the gravitational pull of the moon and sun. The heat from radioactive decay is particularly important as geologists estimate that about half of the Earth's current internal heat comes from the decay of radioactive isotopes within the Earth's interior. Unlike these sources, solar radiation primarily affects the Earth's surface temperature rather than its internal heat and thus did not significantly contribute to maintaining the Earth's early molten interior.