"many speculations" is correct and usable in written English.
You can use it when you want to express that there is a variety of thoughts, ideas, or theories about a certain topic. For example: "The discovery of the new planet sparked many speculations about its origin."
Their origin is not known; among many speculations are that they were brought to northern Europe by westward-migrating (possibly Celtic) tribes or that they developed indigenously.
There has been extensive research in recent years on the multi-scale nature of hippocampal place cells and entorhinal grid cells encoding which led to many speculations on their role in spatial cognition.
For the past few months, there have been many speculations about our future as an independent company.
Many speculations about atoms in the seventeenth century came from a source quite distinct from mechanical atomism.
There have been many speculations about whether there have been overdiagnosis and overtreatment, creating a lot of arguments and confusion.
Although there are many speculations about the future of the peace process, but it would be difficult to drastically change the peace process or, revert back to war.
Mr. Ross's choice of Assured, based in Bermuda, surprised many; speculation earlier this year pointed to Ambac as his likely target.
MBNA is already said to be in play, with many speculation that Wachovia is its likely buyer.
During the time of the video's release, Carey and Mottola were in the midst of their divorce and this led to many speculation on the video's message.
And all this after growing up poor in my grandmother's half-starving canned green-peakitchenand after surviving Depression and War how did she garner so much abstruse lore onredistributionhow accrue so many practical speculations about what we'd need to correct these failuresand flops?
Although Tegmark rejects many current speculations that bemuse lay people (eg quantum consciousness; humans as simulations in some alien's computer game), he constantly returns to a notion equally outlandish: a version of quantum mechanics that implies countless clones of ourselves inhabiting parallel universes.
